Abstract:
A screening parameter was introduced into the enhancement factor used to calculate
positron annihilation rates based on the perturbed hypernetted chain approximation model. The
consequential effects of electron-positron screened pseudopotential on positron annihilation rates
in metals were thereby studied. The results obtained for the annihilation rates were in very
satisfactory agreement with experimental values for alkaline, alkaline- earth, some transition and
noble metals. It was also revealed that high annihilation rates were recorded in metals in which
the electron-positron screened pseudopotential is small and vice-versa. The study further
revealed that electron-positron correlation energy due to screening in metals decreases the total
electron-positron correlation energy (as it has a smaller value than the total electron-positron
correlation energy) and it varies in the same manner with the eleq;on gas parameter as the
electron-positron correlation energy. On the total potential experienced by positrons in metals,
the study showed that electron-positron correlation potential has the minimum contribution to the
total potential and it increases with an increase in the electron gas parameter. Also, the total
potential has the highest contribution from the electronic potential for alkaline, alkaline-earth and
simple metals while the highest contribution for transition metals is from the ionic potential.
From the study. an interpolation expression was put forward for calculating the total potential
experienced by positrons in metals.
